God I love sports manga that actually teach strategy about the sport its portraying. Not only do opposite handed hitters have an advantage naturally, but slider heavy pitchers are especially prone to this because their main weapon, the Slider, is neutralized because its sweep is so easily seen by an opposite handed hitter. If it's outside trying to dart back inside the zone for a strike? It helpfully breaks right into the batters bat. Is it outside and you want it to stay outside? You have to throw it so far off the plate that it makes it easy to see and lay off of. Throwing a backdoor slider inside? You're risking a Hit-by-pitch if you overdo it.